This invention relates to a system for the automated handling of semiconductor integrated circuit packages from supply tubes used in the transportation and storage of the integrated circuit packages. The invention particularly relates to the receiving, orienting and movement of symmetrical supply tubes and the subsequent discharge of integrated circuits packages from those tubes into a selected position and orientation.
2. Description of the Prior Art
Semiconductor integrated circuit packages (hereinafter referred to as integrated circuits or IC) present an unusual packaging and handling situation because of their small size, fragile nature, and, often, large quantity. Their inception created a need for a package to facilitate the transfer and handling of large numbers of IC between manufacturing and testing processes and, ultimately, for storage and shipment to their place of use. The development of the hollow IC supply tubes (also known as magazines, carriers, and sticks) was in direct response to that need. The tubes are available in various constructions but generally are manufactured of extruded plastic in an open-ended form approximating the shape of the workpiece to be contained within. The tubes effectively protect the IC, facilitate their inventory, and preserve a desired alignment of the IC for subsequent processing. They are universally used in the handling, shipping, and storage of IC. The adoption of the tubes as the vehicle of choice for IC has created a subsequent need for machinery to facilitate the handling of the tubes.
The dual in-line package, or DIP, shown in FIG. 1A has historically been the most popular and widely produced IC. DIPs are generally rectangular in body with thin, rather fragile leads extending from the body a sufficient distance to be plugged into a circuit board. The A-tube shown in FIG. IB was developed specifically to accommodate the unique character of the DIPs. The A-tube is shaped like the perimeter of an "A" in that it is narrower at its flat peak than at its base with sides sloping outwardly from peak to base. The interior void of the "A" is shaped to closely conform to the shape of the DIP in a manner which distributes the weight of an individual IC, or a line of ICs, upon the DIP body rather than upon the bendable leads whether in the upright "live bug", inverted "dead bug", or on-end position.
A variety of factors including the commercial importance of the DIP and the competitiveness of the IC market operated to make the A-tube the focus of industry efforts to automate the handling of ICs. However, it is the asymmetrical shape of the A-tube itself which has enabled mechanical manipulation of a storage tube in such a way that it could be reoriented with certainty and consistency and its contents could subsequently be discharged in a preselected alignment. The external configuration of the A-tube both reflects the orientation of the chips within and facilitates the mechanical selection of a particular orientation of the tube.
Prior art has employed many different approaches to achieving a specific rotational position of A-tubes. One method rotates a drum through a bin of agitated A-tubes and singulates the tubes into an indexed position by thus urging the tubes into narrow slots on the drum which will accept only the peak sides of the A-tubes. Another method reorients A-tubes by floating them on jets of air where the tubes will seek a certain position as a result of their center of gravity. Another method singulates the tubes to any rotation and then individually turns them through a break beam sensor to determine the desired rotation. All the methods available in prior art rely on the asymmetrical shape of the supply tube to index the tube for automated handling. An automated system for handling irregularly shaped tubes is disclosed in U.S. Pat. No. 4,878,801.
Many IC packages developed more recently than the DIP do not share its unique shape. Single in-line package, SIP, and zigzag in-line package, ZIP, provide plug-in length leads which extend from a single side of the package. Small outline J-bend, SOJ, such as shown in FIG. 2A and plastic leaded chip carrier, PLCC, provide shorter leads which are bent back against the body of the package and are surface mounted rather than plugged into a socket. Leadless chip carrier, LCC, style packages have no lead extensions but, instead, provide sockets whereby they may be connected to a circuit board. A wide variety of other styles of packages exist which provide their own specific advantages and characteristics.
The more recently developed surface-mount technology, SMT, packages (for example the SOJ, PLCC, and LCC) are generally more symmetrically shaped than the DIP and without fragile extended leads. Packages such as the SOJ, the PLCC, and the LCC have relatively shortened or no leads. An asymmetrical tube is neither necessary nor desireable for these chips. Their symmetrical tubes, however, pose a sensing and handling problem. "Symmetrical tube" in this context is used to mean a rectangular tube, similar on two opposing sides (refer FIG. 2B). Where the interior articles are oriented in a particular manner, the tube is the same to devices sensing the outside of the tube. For example, a symmetrical tube standing on either side, full of SOJ chips uniformly in line, would have the SOJ leads facing either left or right. Unlike the asymmetrical A-tube, symmetrical tubes in themselves are not outwardly distinguishable as to either of two sides nor are they susceptible to mechanical urging to a particular position.
The inventive device enables automatic handling of symmetrical IC supply tubes such that articles contained within may be discharged in a desired orientation. The principal distinction over prior art is the ability to automatically sense and reorient the IC without dependence on a unique quality of the supply tube.